A colleague from the Northeast once said during the dinner: The Mohe River in winter is frozen with ice. If you walk on it in the middle of the night, you will see the black sky above and black ice below. They are both bottomless and you don't know what the sky is and what the earth is. It is very scary.
Can't help but wonder, who is it? For what? Are you going to risk your life and come out on the ice in the middle of the night? What else did he find on it? Hence the story "Ye Lai".